Archive for the ‘Chemistry World’ Category

Glass transition in ant traffic jams

Inspired by the fluid-like motion of flocks of birds, researchers in the US have used techniques from soft matter physics to study the way that fire ants move.

At high density collective ant flow can be described by the physics of glass-forming soft materials © Shutterstock

Collective motion is ubiquitous in nature. Fire ants in particular provide a fascinating case study due to the confinement enforced by the foraging tunnels in which they move. A key factor in the motion of fire ants, and other eusocial insects, is the requirement to stop and communicate with each other, leading to traffic jams and blockages along the 50m long underground superhighways in which they travel.

To read the full article visit Chemistry World.

Glass-like dynamics in confined and congested ant traffic
Nick Gravish, Gregory Gold, Andrew Zangwill, Michael A.D. Goodisman and Daniel I Goldman  
Soft Matter, 2015, Accepted Manuscript
DOI: 10.1039/C5SM00693G, Paper

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Caddisfly silk gets shocked into self-recovery

The tough, extendable, energy-dissipating properties of the casemaker caddisfly’s adhesive silk are down to a self-recovering network of calcium crosslinks, new research shows. US researchers behind the discovery hope to harness these findings to design new synthetic bioadhesives that can adhere to wet tissues.

Images (l and m) of silk holding together glass beads in the same way that silk and stones combine to make the body armour (r)

To read the full article visit Chemistry World.

Self-recovering caddisfly silk: energy dissipating, Ca2+-dependent, double dynamic network fibers
Nicholas N. Ashton and Russell J. Stewart  
Soft Matter, 2015, Advance Article
DOI: 10.1039/C4SM02435D, Paper

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Making light of food allergies

Researchers in Spain are taking steps towards ‘allergy-free’ food, by treating allergy-inducing proteins with a pulsed light treatment that makes them easier to digest.

 The scientists at the University of Granada and the AZTI-Tecnalia Food Research Institute studied the protein β-lactoglobulin, which acts as an excellent emulsifier in milk and other food products but has a compact structure that defies easy digestion. This lack of digestibility is linked to allergenicity, explains team member Julia Maldonado-Valderrama: ‘If the protein is not completely digested, the body reacts as if it is an allergen, which can trigger an allergic reaction.’ Pre-treatment could break down the protein structure before eating; however, it’s a balancing act. ‘If you break the protein down too much in order to facilitate digestion, they lose their functionality and can’t be used to make foams and emulsions in food products,’ says Maldonado-Valderrama.

To read the full article please visit Chemistry World.

Improved digestibility of β-lactoglobulin by pulsed light processing: dilatational and shear study
Teresa del Castillo-Santaella, Esther Sanmartín-Sierra, Miguel Cabrerizo-Vílchez, J Arboleya and Julia Maldonado-Valderrama 
Soft Matter, 2014
DOI: 10.1039/C4SM01667J, Paper

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Colloidal caterpillars get a wiggle on

Researchers have devised a new method to transport micro cargo – by attaching it to chains of colloidal particles that wiggle their way through liquid crystals.

The research team, led by Hiroshi Orihara from Hokkaido University, Japan, and Christian Bahr from the Max Planck Institute for Dynamics and Self-Organization, Germany, created colloidal ‘caterpillars’ from surface-modified silica particles which self-assemble into chains when placed in a liquid crystal medium. To make them move, the team exploit an effect called electrohydrodynamic convection (EHC), where the application of an electric field creates a convective pattern of parallel rolls within the medium. The caterpillars travel in an undulating motion across successive rolls, driven by a combination of hydrodynamic flow and electric field effects. Excitingly, the caterpillars can be attached to and used to transport larger particles and liquid droplets, which are in themselves too big to be moved by the EHC rolls.

To read the full article visit Chemistry World.

Colloidal Caterpillars for Cargo Transportation
Yuji Sasaki, Yoshinori Takikawa, VSR Jampani, Hikaru Hoshikawa, Takafumi Seto, Christian Bahr, Stephan Herminghaus, Yoshiki Hidaka and Hiroshi Orihara  
Soft Matter, 2014, Accepted Manuscript
DOI: 10.1039/C4SM01354A, Paper

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Soft matter goes digital

Already used in everything from paints to optical materials, colloids have found an entirely new application: as computing elements capable of high density information storage.

US collaborators Sharon Glotzer from University of Michigan and David Pine from New York University have designed a system of reconfigurable colloidal clusters which show potential for performing computational functions in unconventional environments. The team’s ‘digital colloids’ are based on specially designed dimpled particles, which, through entropic interactions, can be made to assemble onto a central sphere and explore various configurations on the sphere’s surface.

To read the full article please visit Chemistry World.

Carolyn L. Phillips, Eric Jankowski, Bhaskar Jyoti Krishnatreya, Kazem V. Edmond, Stefano Sacanna, David G. Grier, David J. Pine and Sharon C. Glotzer
Soft Matter, 2014, Advance Article DOI: 10.1039/C4SM00796D
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A second look at dry eye syndrome

Measurements highlighting the different mechanical properties of healthy and diseased tear film could provide fresh understanding of the underlying causes of dry eye syndrome, and point to new treatments to ease the discomfort of millions of sufferers.

With risk factors including contact lens wear and extended periods in front of a computer screen, the discomfort and visual disturbance associated with dry eye syndrome (DES) is a growing public health concern.

To read the full article please visit Chemistry World.

Surface relaxations as a tool to distinguish the dynamic interfacial properties of films by normal and diseased meibomian lipids
Georgi As. Georgiev, Norihiko Yokoi, Slavyana Ivanova, Vesselin Tonchev, Yana Nencheva and Rumen Krastev  
Soft Matter, 2014,
DOI: 10.1039/C4SM00758A
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Redefining moisturiser – Soft Matter article in Chemistry World

The secret to soft skin is not necessarily increasing its water content but retaining molecular fluidity © Shutterstock

Scientists in Sweden have probed the outermost layer of skin to gain molecular insights into how naturally occurring molecules in this layer protect it from drying out.

Healthy skin with a normal degree of hydration is soft and pliable. This is not the case for dry skin, which is brittle and easily cracks. To treat dry skin it is common to apply a cosmetic containing a humectant  ̶  a type of “moisturiser” – like glycerol or urea. These substances are also components of natural moisturising factor (NMF), a group of molecules naturally present in the skin barrier. The beneficial function of these compounds if often claimed to be their capacity for increasing skin hydration, although the underlying mechanisms are generally described with a rather weak molecular basis.

Interested to know more? Read the full news article by Jennifer Newton in Chemistry World here…

Read the paper by Sebastian Björklund et. al for free until 23 May 2014:

Stratum corneum molecular mobility in the presence of natural moisturizers
Sebastian Björklund, Jenny Marie Andersson, Agnieszka Ewa Nowacka, Quoc Dat Pham, Daniel Topgaard and Emma Sparr
Soft Matter, 2014, Accepted Manuscript
DOI: 10.1039/C4SM00137K, Paper

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Responsive gel stays strong – Soft Matter article in Chemistry World

 The first hybrid gel that is responsive as well as robust has been made by scientists in the UK.

We encounter gels on a daily basis in food, cosmetics and pharmaceuticals. Some gels are very responsive – something can happen to them and they will break down. Some gels are very robust and can survive a lot of stress. Often when a responsive gel responds to a stimulus it breaks down so it is no longer a gel you can do anything with. ‘That’s useful in itself, but you don’t always want that,’ says David Smith whose team at the University of York have developed the new responsive and robust gel. 

One gel network can be assembled and responsively disassembled while the other polymer retains the material’s integrity

 

Interested to know more? Read the full news article by Jennifer Newton in Chemistry World here…

Read the article by  D J Cornwell, B O Okesola and D K Smith in Soft Matter:

Hybrid polymer and low molecular weight gels – dynamic two-component soft materials with both responsive and robust nanoscale networks
Daniel J. Cornwell, Babatunde O. Okesola and David K. Smith  
Soft Matter, 2013,9, 8730-8736
DOI: 10.1039/C3SM51967H, Paper
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A flexible future for robotics: Soft Matter article in Chemistry World

US researchers have created a series of smart materials that twist and coil in response to light. These soft materials could be used in the muscle systems of future robots.

The field of robotics is looking to move beyond the clanking, jerky monstrosities of bad Hollywood movies. Most robotic systems are still hard, composed of metal structures with joints based on conventional bearings. Wheels and treads are often used, unnatural elements that cannot reproduce natural motions. A further limitation is they require large on-board energy sources to power motion, which increases weight and limits portability.

Now, a team including Timothy White and Matthew Smith at the US Air Force Research Laboratory in Ohio, have fabricated a series of cantilevers made from azobenzene liquid crystal polymer networks that can twist and coil, powered only by a change in the polarity and intensity of an external light source. The direction of the resulting torsional movement is partly controlled by the order within the material.

Smith, now an assistant professor at Hope College in Michigan says that while stimuli-responsive materials have exhibited planar and twisting motions before, the aim of the study was to ‘expand the suite of motions available’. The out-of-plane motions developed in this work are essential to ‘drive the field forward’ and better copy the more dexterous movements of living creatures.

Gursel Alici, a robotics expert at the University of Wollongong in Australia says this work ‘makes a significant contribution towards the realisation of biologically inspired robotic systems’. However, he believes ‘there are some immediate questions, which should be addressed before seeing application of this and other similar smart materials in novel device concepts.’ These questions include how to scale up the cantilevered structures to provide mechanical outputs as good as those of skeletal muscles.

Smith agrees that application of these materials in practical robots is far off, but this is only one of many interesting applications for their work. He admits that the main ‘limitation of these materials, right now, is [that] they are confined to small scales’ and thin films.

Future work will aim to produce materials that are capable of more complex motions and that are more mechanically robust for larger scale applications.

Torsional mechanical responses in azobenzene functionalized liquid crystalline polymer networks
Jeong Jae Wie, Kyung Min Lee, Matthew L. Smith, Richard A. Vaia and Timothy J. White
Soft Matter, 2013, Advance Article DOI: 10.1039/C3SM51574E

This feature was written by Jason Woolford and was originally published online in Chemistry World.

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Flat-pack structures build themselves

Scientists in the US have developed flat pack structures that can autonomously assemble into three-dimensional shapes on application of an electrical current. Unlike traditional three-dimensional assembly techniques, which require sophisticated printers to reach the final product, this approach uses heat triggered shape memory polymers.

Three-dimensional structures normally come pre-assembled or equipment needs to be transported to create them in situ. Now, along with his colleagues, Samuel Felton, from Harvard University, has demonstrated that by printing shape memory polymers (SMP) onto laser-cut joints with conductive coatings, the assembly process can be separated entirely from the original printing.

Initiation of the SMP transformation is central to Felton’s technique. A SMP is printed in a deformed, flat state and aligned with a resistive circuit over a scored substrate, in this case, paper. An electric current is then run through the circuit and joule heating activates the phase transformation of the shape memory polymer back into its original shape and folds the paper. As this combination is electrically triggered, it allows both simultaneous and sequential folding of complicated shapes.

Felton explains that the most challenging aspect of the work was creating the precisely aligned composite as the approach relies upon separately cut layers that are then joined using a mixture of pins and silicone tape. As alignment is performed when manufacturing the flat structure, the end product is, as was the aim, ‘accessible for everyone.’

Jinsong Leng, an expert in smart materials at Harbin Institute of Technology, China, agrees: ‘shape memory composites play an enormous role in self-folding structures formed by remote and automated assembly. The approach could significantly accelerate the advancement of promising applications in 3D structure fabrication techniques.’

Self-folding with shape memory composites
Samuel M. Felton, Michael T. Tolley, ByungHyun Shin, Cagdas D. Onal, Erik D. Demaine, Daniela Rus and Robert J. Wood
Soft Matter, 2013, Advance Article

This feature was written by Charlie Quigg and was originally published online in Chemistry World.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

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